Negative testing deliberately exercises conditions outside the normal successful path. It can include empty required fields, malformed values, denied permissions, unavailable services and actions performed in the wrong order.
The goal is to verify safe, understandable failure behavior. The application should reject invalid operations, preserve valid data and give the user an actionable response rather than crashing or silently corrupting state.
ELI5
Negative testing asks, what happens when the input is wrong or something important is missing? It checks that the application handles mistakes safely.
For example, a tester may submit a form with an empty email field and confirm that the page explains the problem without losing the other entered information.
